Thread severing device for sewing machines



s- 2, 1958 .1. DOERR EIAL 2,846,967

THREAD SEVERING DEVICE FOR SEWING MACHINES Filed Dec. 9, 1955 3She'ets-Shee't 1 Wyn/r025 Aug. 12,195 3. Dom- ETAL may: 'SEVERING DEVICEFOR SEWING MACHINES Filed Dec. 9, 1955 5 Sheets-Sheet 2 M Q m a w. p Q.5%.. mm qw y MN: l g R Q M w .i a 4 J h s flOEPP Mlbe/m pen/ER 1953 J.DOERR ETAL 2,846,967

THREAD SEVERING DEVICE FOR SEWING MACHINES s sheets-sheet 3 Filed D60.9, 1955 INVENTORS: Jo6ann?s 8 and lA/rlfi'elm Drake, BY [J aTHREADSEVERING DEVICE FOR SEWING 'MAICHINES Johannes Doerrand WilhelmDreher, Kaiserslautern,

Germanyaassignors to Gt M.:Pfaff A.-G., Kaiser- .slautern; Germany, acorporation of Germany ApplicationDecember 9; 1955,'"Serial No. 552,085

Claims priority, application Germany December '10, 1954 12Claims. (Cl;1l2252) The-.invention relates .to. sewing-machines, and relates more.particularly to athreadsevering device for-use in connection with asewing machine.

Still more particularlyythe invention-relates -to a-thread severingdevice .fon-cuttingthe upper-thread as well-as the lower thread ona-sewingamachine.

. The invention has among its objects to provide for the severance-cfthe upper land'rlower'threads of asewing .machine, characterized' bysimple means of actuation and subsequent automatic thread release.

.. his a further'objectof the. invention to provide'such .a. devicewhich-will cut the upper and lower threads adjacent the uppernandtlowersurfaces of the work-piece. It is a stillsfurther objected-the inventionto provide such a device which .will. first clamp thethreads,-thereafter cutithem, vanclsubsequently release them.

The foregoing andother-= objects of the invention-will be. bestunderstood. from, i the following description of.exemplification"thereof, referencebeing had to-theaccornpanying.drawings,- wherein:

Fig. 1 isaa fragmentary perspective view'ofasewing machineswith: abuilt-in thread-severing device in accordance with-theinventiomtheneedle plate has been removed in the illustrationof Fig. 1 to exposetheparts below the needle plate;

Fig.2 is an. underside perspective view of the needle plateincluding-the.parts'ofthe devicefor'use in severing .the. lower. thread;

\Eig. .3:is.an=extended perspective view-=01? the needle severing.device;

"Fig-4. isaa sectional viewofthe needle. plate, taken :01]. line.IV-.-IV of Fig. 2;

Fig 5. is :a large scale fragmentary vertical sectional view, .taken .online VF-Vcf Fig. 1, showingthe parts inv position during the first stepof the severingoperation;

Fig.- 6 .is... a: fragmentary plan view, partly in'section,

taken. on line- VI-VI of vFig.

Fig. 7 is a fragmentary large scale vertical sectional view similartoFig. 5; butshowingthe'parts :positioned as duringthe second step ofthe-severingoperation, when thethread is. actually cm;

Fig. 8'..is1.a.. fragmentary; plan view, partly 'in'section taken. online-.VlIL-VIII of :Fig. 7;

'Fig. 9 is a fragmentary :l'arge-scale vertical sectional view similarto. Big. 1,= buthshowing'ftheparts released after thread 1 cutting;

Fig/1011s .a fragmentary plan view," partly in" section taken on lineX-1X"ofEig. 9;

Eig..11-.is:.an elevational view ofasewing machine :with-a thread'severing device in accordance withfthe invention.

:In" carrying 'the'invention' into effect? in one of the embodimentswhich has been selected for illustration mithe accompanying :drawingsand for description in "this-specification, and: referring nowparticularlyto Figs.

1-3, there is provided a sewing machine that isrsupported one work table1, and comprises an arm-Zandahead 3.

United States PatentO facing recesses 24anda rearwardtfacing groove25.The

351 in alignment-with, the recesses -24 of'theh-'flange 23:0f

2,846,967 Patented Aug-- 12,

A' needle'bar 4,-and a presserbar- 5 for a sewing foot, are journalledfor reciprocal movement the head 3.

Thecpresser bar 5 operates a'thread- 'tensioner 6-as well with asectional s1ot16 whichincludesa needle-hole '17.

In thebottom surface of the body -11. there is=-formed a guide recess inwhich there is guidedifor reciprocating sliding movement a slide19(Figs. 3 and 5). Fheslide 19 carries on its=front endonouter-visefijaw-l0athat has a rear'edgezl. Adjacenttherear edge-21 thereis formed onthe slide 19a slot-22 (Figs: 3 and 6:) which -extends froma-lateral-edge of the slide-19 inwardly to a point mid-way-of thewidthofthew' slide: 19-. The

rearedge 21 as :well---as'-the:slot"22 are inclinedrelative to i thedirection of reciprocation 0f the slide 19; as :best :shown inFig. -6.On'therearend; theslide 19 carries a flange v23; (Figs. 3, 5, and-.7)which has two-forward vise jaw 20 carries a pin 26 (Figs; 3-.a-nd 6),whichvcan abut against the lower front surface ofthebody 11*(Fig.

' 8) .to limit the rearward movement oftheslide-19.

A plate 27 is-mounted tothe underside of the body 11; it is formedon-its front as va-c-utter-ZS,- andthecon- -necti0n to the-body.11-maybe-madei'by screws, for-instance byscrews 27a (Fig. 3). The body-11-has-two recesses 29 (Fig. 7) whieh aredisposed opposite to,and

the slide 19. Compression springs 30 (Figs. 3 and7) are disposed in theopposite recesses-24 and 29 and normally urge :the slide 19 into "-therearwardmost position (Fig. 7)- wherein-the, pin 26 abuts against thebody- 11.

An inner vise jaw-31 (Figs.- 3 and 5) is? carried'at'the forward end ofa.rod-32, ands-the rod--32-=is--guided for reciprocation in the body 11.The-innervise' jaw e31 is in sliding engagement with- 1 the top=vsurfaceof the slide 19, rearwardly of theouter'viseijaw20,-- and-:co-'operates with'the saidouter-vise jaw 20 .fOF'I-6183S3blY clamping theupper -thread. The rod32 extends to-"the hollow interior ofthe body andhas onrthe'rear end portion an-annular. groove 33 (Fig-3). -A' leaf'spring 34 (Figs. 3 and 7) has on its lower-end a bifurcation whichengages the groove 33 of the rod 32. The spring 34 'isidis'poseduprightly, and'is connected with its upper "end to the'body 11 by meansofa-screw 35. The 'rod 32'and the inner vise jaw 31 are movable between:a forwardmost position (Fig. 5)--andta rearwardmost'positron (Fig. 9-).

'The body-11 has a vertical-hollow chamber, into.

which there extend therear portions of the-slidew 19 and of" the'rod 32.The spring- 34 is disposed in 'the chamber 36. In this chamber 36-thejrewis furthermore tiltably movable a reciprocable lever-38; (Figs.-3:and"5) which is pivoted at37. The reciprocable 1ev'er"38 istiltable'between two extreme positions.namely an active position (Fig.5) whereinits..-1ower end-is disposed torwardmost, and aninactiveposition (Fig. 9 )"wherein its lowermost end is disposedrearmost. The lower part 39- ('Figs. 3 and 5) ofthelever 38 engages-thegroove '25 of the flange 23. The upper part of the lever-38 -is curvedand forms a cam follower 40 for acarn roll 43.

The roll 43 is carried on a tiltable retractable actuating lever 42(Figs. 3 and 5) which'is pivoted with its .forward 'end'about 'a'pin 45-'in a recess 44 to the body 11.

The lever 42 base slot- 41*th1'0ugh'" which'there extends the camfollower 40 of the lever 38. The actuating lever 42 to the set position(Fig. 5) is controlled by a lifting mechanism'49 that includes a rope orcable 48 that engages with a loop 47 (Fig. 3) the free end of the lever42. The lifting mechanism 49 may be controlled from electromagneticactuating means 87 (Fig. 11). When the lifting mechanism is released,the springs 30 will turn the lever 38 in the opposite direction, therebyreturning the lever 38 as well as the tiltable lever 42 to theirinactive positions. The lifting mechanism 49 includes a tube 51 seatedin a tubular extension 50 of the body 11.

A tiltable member 52 is hinged to the body 11 and has its major portiondisposed frontwardly of the face of the body 11. The tiltable member 52includes two parallel lugs 53 that extend into the frontal recess 44 ofthe body 11 and are pivoted to the body 11 about a pin 54. The pin 54 isdisposed lower than the pin 45 of the lever 42. The tiltable member 52is provided with a central upright slot 55 and has a horizontal groove56 formed in the front face above the slot 55. The lower part of thetiltable member 52 is provided with lateral flanges 57 (Fig. 3) againstwhich there abut from the rear two pressure rods 59 which are slidablyguided in horizontal bores 58 of the body 11. The pressure rods 59extend rearwardly into the hollow chamber 36 of the body 11, and theirrear ends extend into the path of lateral flanges 60 which are formed onthe lower end portion of the lever 38. A rod 61 is provided which isguided in a horizontal bore 62 of the body 11, and disposed mid-waybetween the pressure rods 59 and located below the same. The front endof the rod 61 is disposed for abutment with a bridge portion of thetiltable member 52 that is formed below the slot 55 thereof, and therear end of the rod 61 extends to the chamber 36 and is adapted to abutagainst the front face of the upright leaf spring 34.

A compression spring 63 (Fig. 5) extends from a recess that is formed inthe front surface of the body 11, and exerts pressure with its front endagainst the top portion of the tiltable member 52, urging the latterinto a rest position (Fig. 9) wherein the tiltable member 52 pressesrearwardly the pressure rods 59 and the rod 61, whereby the rods 59 willpress rearwardly the lower portion of the lever 38, and the rod 61 willpress rearwardly the lower end of the leaf spring 34.

A latch member 65 (Figs. 3 and 5) extends through the slot 55 of thetiltable member 52, and has an extension 66 which is pivoted about thepin 45 to the body .11. The upper end of the latch member 65 forms arearwardly projecting finger 67 which is adapted, when in the activeposition (Figs. 5 and 7), to engage the groove 56 of the front face ofthe tiltable member 52. The lower forward end of the latch member 65 ispointed frontwardly and forms a nose 68 which is adapted to cooperatewith the needle bar 4; the nose 68 projects in the active position ofthe latch member 65 (Figs. 5 and 7) into the path of the needle bar 4,and may be engaged by the needle bar 4 to tilt the latch member 65 intothe rest position (Fig. 9) thereof.

A spiral spring 69 (Fig. 5) surrounds the pivot pin 54, and exertspressure with one arm 70 against the lower edge 71 of the slot 44 of thebody 11, and with its other arm 72 exerts pressure from the rear againstthe latch member 65. The spring 69 tends to turn the latch member 69into the active position (Figs. 5 and 7).

On the underside of the needle plate 8 (Figs. 2 and 4 there is mounted athread severance device, of conventional construction, for the lowerthread 84. It comprises a guiding groove 72 that extends at right angleto the work feeding direction A (Fig. 1). A cuttlng knife 73 (Fig. 4) issecured to the needle plate by means of a counter-sunk screw 74. A slide76 18 m a sliding engagement with the cutting knife 73, and is guided inthe groove 72, and includes a hook 75. A spring 77 presses the slide 76towards the cutting knife 73. A pin 78 extends downwardly from the slide76, and projects into a slot 79 of one arm of a lever 80 that isjonrnalled on the underside of the needle plate 8. The other arm of thelever 80 is connected to a pulling device 81 and to a retraction spring87.

The operation of the above described device is as follows:

A work piece 85 (Figs. 5, 7) is provided with a seam 86. The needlethread or upper thread 83, and the lower thread 84, are to be cut off.As a first step, the operator will move the needle bar 4 approximatelyto the topmost position (see Fig. 5) and thereafter will cause the cable48 to be pulled upwardly to lift the lever 42 into its horizontal upperposition (Fig. 5). The lifting of the cable 48 of the lifting mechanism49 may be accomplished by the actuation of the electromagnetic actuatingmeans 87 to which the cable 48 is connected. The lifting of the cable 48causes turning of the tiltable lever 42 from the rest position (Fig. 9)to the set position (Fig. 5).

During the upward tilting movement of the actuating lever 42, the roll43 thereof will push to the rear the cam follower portion 40 of thereciprocable lever 38, thereby tilting the lever 38 about the pivot 37,from the inactive position (Fig. 9) to the active position thereof (Fig.5). The lower part 39 of the lever 38 engages the groove 25 of theflange 23 of the slide 19, and during the tiltingto the active positionwill push the slide 19 together with the outer vise jaw 20 forwardlytowards the upper thread 83. In the raised position of the needle bar 4(Fig. 5) the upper thread 83 is tensioned vertically and, when the slide19 is pushed forwardly, the upper thread 83 will be engaged by theinclined slot 22 of the slide 19 (Figs. 5 and 6).

During the tilting movement of the lever 38 to the active position, thelateral flanges 60 thereof will push forwardly the pressure rods 59,causing rotation of the tiltable member 52 from the rest position (Fig.7) into the active position (Fig. 5). This turning of the tiltablemember 52 is about the pivot 54, and against the pressure of the spring63. During this turning of the tiltable member 52 to the activeposition, the latch member 65 will, under the pressure of the spring 69,be tilted about the pivot pin 45, and will engage with its finger 67 thehorizontal groove 54 of the tiltable member 52, coming to rest in theactive position in which the nose 68 projects into the vertical path ofthe needle bar 4 (Fig. 5).

By the forward movement of the lower part of the tiltable member 52, therearward pressure that had been exercised against the rod 61 will bereleased, thereby releasing the leaf spring 34 which will push forwardlythe rod 32 and thereby place the inner vise jaw 31 in the forwardrnostposition (Fig. 5).

Upon release of the pedal (not shown) of the lifting mechanism 49, thelever 42 will be released and will rotate downwardly about the pivot pin45 to its rest position (Fig. 7 Thereupon the springs 30 will retractthe slide 19, and the latter will return the lever 38 from the activeposition (Fig. 5) into the inactive position (Fig. 7).

The upper thread 83 which passes through the slot 22 (Fig. 6) will bythe rearward movement of the slide 19 first be pressed by the outer visejaw 20 against the inner vise jaw 31 which is pressed forwardly by theleaf spring 34. Both vise jaws 20 and 31, which form clamping means forthe upper thread 83, thereafter will slide together rearwardly for adistance while still gripping the thread 83, until the outer vise jaw 20is arrested in its rearward estless? :zmovement byttheabutment. impact1between the'pin 26 atmtlzthelower front surface of the body'11,-(Figr8).' During this a-tied rearward: movmnent of the two :jaws,the

28 to sever the upper thread 83.

After the lever, 3& has been returned to the inactive position (Fig. 7),the ;latch member-:65 will-'stillsremain in the upwardly tilted position'wherein its nose .68'projects' t forwardly. into the I, path\ofzthexneedle .bar.

Simultaneously with-the .cuttingiof thenpper thread. 83 there will becut the lower thread 84. The electromagnetic actuating means 87 whichactuatesthe pulling mechanism 49, also. pulls at .thesame time the,pulling devicev 81 (Fig. 2),-to'tilt' the lever '80 to move thereby thehook 75 ofithe'1slide v76.tovvards..t-he.needle path until the slotbehindzthe hook.75 is positioned in registry with the stitching holeofzthe needle. plate..8. .The hook 75 will engage ;the lowerzthread .84and, uponrelease ofthe pulling device .81, the spring .87 willretract.the slide 76 and the thread 84 will be cut by the knife 73. The end ofthe lower thread 84 will be engaged between the spring 77 and theunderside of the slide 76.

The pressure foot 10 may be lifted in a conventional manner for theremoval of the work piece 85, and work may be resumed thereafter at anydesired place of the Work piece 85 following lowering of the pressurefoot 10.

When the work on the sewing machine is resumed by the needle 82, theupper thread 83 will remain gripped between the jaws 20 and 31 (Fig. 7)until the needle bar 4 by impact actuation with the nose 68 returns thelatch member 65 to the rest position (Fig. 9). Upon such impact, thefinger 67 will be moved out of the groove 56 and will be positioned asshown in Fig. 9. At the same time, the movable member 52 will be tiltedby the force of the spring 63, whereby the rod 61 will again tension theleaf spring 34 causing a further rearward movement of the inner jaw 31(Figs. 9 and 10). By this further rearward movement of the inner jaw 31,the vise grip of the upper thread 83 will be released, and the thread 83thereafter be moved by the needle 82 into the work piece 85 almost toits severed end, rendering possible the forming of a new seam afterpicking up the lower thread 84.

We wish it to be understood that we do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

Having thus described the invention, what we claim as'new and desire tobe secured by Letters Patent, is as follows:

1. In a thread severing device for sewing machines having a pressurefoot and a needle plate and a needle bar carrying a needle, incombination, a first mechanism disposed below said needle plate forsevering the lower thread, and a second mechanism operable for severingthe upper thread and comprising a body connected to said pressure foot acutter connected to said body and a releasable vise including jawsguided in said body for movement adjacent said cutter reciprocably inopposite directions towards and from the path of said needle andengaging and being settable for gripping said upper thread, said viseand cutter cooperating for severing said thread, means operable formoving said jaws from a rest position towards said needle path, andresilient means urging said jaws to return to said rest position, viserelease means connected to said body and being movable between an activeposition wherein it projects into the path of said needle bar and blocksthe return of one jaw and, respectively, an inactive position wherein itis spaced from said path and unblocks said one jaw, and means movingsaid release means into said active position during movement of saidvise towards the needle path, said needle bar actuating said releasemeans by impact during the last phase of the next succeeding downwardstroke to return the release means to'the inactive position thereby toreleaseusaid vise.

' 2; In a thread severing device for-sewing machines having a pressurefootand a needle plate and a vertically movable needle bar carrying aneedle, in combination, a

first mechanism disposedbelowsaid needle plate for severing the lowerthread, and a second mechanism connected tosaid pressure footandoperable' for severing the upper thread-and comprising a bodyconnected to said pressure foot, avcutter connected to said body, andreleasably 'actuatable thread clamp means guidedin said bodyand beingadjacent: said cutter movable towards, and retract- ..able from,thepathwof said needle for first clamping said thread, said clamp. meanscooperating-with'said ..means urging.said-jawsJto'returnto said restposition,

vise .release'means :connected. to said body and: being mov- 1 ablevbetween. an: active position'wherein it projectsinto the path of saidneedle bar and blocks the return of one jaw and respectively, aninactive position wherein it is spaced from said path and unblocks saidone jaw, and means moving said release means into said active positionduring movement of said vise towards the needle path, said needle baractuating said release means by impact during the last phase of the nextsucceeding downward stroke to return the release means to the inactiveposition thereby to release said vise.

3. In a device as claimed in claim 2, together with, means for actuatingsaid clamping meam comprising a retractable first lever pivoted to saidbody and including a cam, a reciprocably movable second lever movable toand from a position of engagement with said clamping means and operableto actuate the same upon engagement and including a cam follower forsaid cam and operable to be moved by said first lever to said positionto actuate said clamping means to engage said thread, and resilientmeans operable to return said second lever and to close and to retractsaid clamping means following retraction of said lever.

4. -In a device, as claimed in claim 2, the underside of one of saidvise jaws forming a shearing head cooperating with said cutter to seversaid upper thread.

5. In a device, as claimed in claim 2, said vise release means includinga tiltable member pivoted to said body for tilting about a horizontalaxis, and a latch member pivoted to said body and operable to be tiltedfor setting together with said control member and having a noseprojecting in the set position into the path of said needle bar.

6. In a device, as claimed in claim 5, said tiltable member havingparallel of its tilting axis a groove, said latch member being pivotedat a point below the pivot of said tiltable member andincluding a fingerengaging in the set position said groove to latch said tiltable memberin said position.

7. In a device, as claimed in claim 5, together with, resilient meansurging said latching member towards the set position and urging saidtiltable member from the set position.

8. In a thread severing device for sewing machines having a pressurefoot and a needle plate and a needle bar carrying a needle, incombination, a first mechanism disposed below said needle plate forsevering the lower thread, and a second mechanism operable for severingthe upper thread comprising a body connected to said pressure foot, acutter connected to said body, and thread clamp means guided in saidbody for movement adjacent said cutter towards and from the path of saidneedle and being operable for clamping the upper thread and subsequentlycooperating with said cutting means for thread severing and thereafterreleasing the upper thread, said clamp means including two jaws,resilient means urging said jaws to close, means for moving one jaw toengage said thread and subsequently releasing it for gripping the threadbetween said jaws, resilient means operable for moving said clamp meanswith closed jaws past said cutter for thread severance and means formoving the other jaw away from the first to release the threadthereafter, said means for moving said other jaw including a tiltablemember pivoted to said pressure foot and tiltable between a set positionand a clamp releasing position, a spring connected to said other jaw andnormally urging said other jaw towards said one jaw, and a rod guided insaid pressure foot and operable to be moved by said tiltable member uponrelease thereof into abutment with said spring to move the same againstits tension to move said other jaw away from said one jaw therebybreaking the grip of said clamp means.

9. In a device, asclaimed in claim 8, together with, means for settingsaid tiltable member comprising at least one pressure rod guided forshifting in said body and operable to abut against said tiltable memberfor tilting it into the set position, said means for moving said one jawincluding a movable lever, an extension formed on said lever, saidpressure rod extending into the path of said extension, whereby saidextension of said lever will shift said pressure rod to set saidtiltable member.

10. In a device, as claimed in claim 8, together with, abutment meansbetween said one jaw and said body for limiting the movement thereof inthe direction from said needle path.

11. 'In a device, as claimed in claim 8, together with, pulling devicesfor said mechanisms operable from the exterior of said sewing machine.

12. In a device, as claimed in claim 11, said pulling devices comprisingelectromagnetic pulling means.

References Cited in the file of this patent UNITED STATES PATENTS952,010 Kiewicz Mar. 15, 1910 1,816,308 Allen July 28, 1931 1,962,905Miller June 12, 1934 2,077,531 Pudelko Apr. 20, 1937 2,707,927 Artzt etal. May 10, 1955

